Test and learn is set of Agile practices that allows a business to test with real customers, real products, to understand impacts on experience and productivity. From there, you learn what needs to be improved, and you do it repeatedly. It is efficient, cost effective, and delivers a greater return on investment.
When testing and learning, we see where there is resistance to the direction of the product or service development we had planned, and when there is, we do further tests to see if there are things we can work around. When we do not meet resistance, we continue to build our product or service one step at a time, constantly sense checking to understand if we are still heading in the right direction.